计算一段日期内的周末天数的php代码（星期六，星期日总和）

http://www.jb51.net/article/20886.htm
加入$is_workday 参数，可以选择是否返回工作日，默认是返回休息日

    function get_weekend_days($start_date,$end_date,$is_workday = false){

        if (strtotime($start_date) > strtotime($end_date)) list($start_date, $end_date) = array($end_date, $start_date);
        $start_reduce = $end_add = 0;
        $start_N = date('N',strtotime($start_date));
        $start_reduce = ($start_N == 7) ? 1 : 0;
        $end_N = date('N',strtotime($end_date));
        in_array($end_N,array(6,7)) && $end_add = ($end_N == 7) ? 2 : 1;
        $alldays = abs(strtotime($end_date) - strtotime($start_date))/86400 + 1;
        $weekend_days = floor(($alldays + $start_N - 1 - $end_N) / 7) * 2 - $start_reduce + $end_add;
        if ($is_workday){
            $workday_days = $alldays - $weekend_days;
            return $workday_days;
        }
        return $weekend_days;
    }